AU2013213724B2

AU2013213724B2 - Rapid load capacity test

Info

Publication number: AU2013213724B2
Application number: AU2013213724A
Authority: AU
Inventors: Justin Williamson
Original assignee: Patented Foundations Pty Ltd
Current assignee: Patented Foundations Pty Ltd
Priority date: 2012-08-14
Filing date: 2013-08-07
Publication date: 2018-01-18
Anticipated expiration: 2033-08-07
Also published as: AU2013213724A1

Abstract

A rapid load capacity test method for piles (including screw piles, blade piles and in-situ cast piles) employs a test apparatus with a mobile test rig locatable 5 about the pile to be tested. A lifting rod is connected to a load-applying jack and is releasably connected to the shaft of the pile. An up-lift load is applied to the pile shaft, and from the force applied, the load-bearing capacity of the pile can be calculated. It (0

Description

COMPLETE SPECIFICATION STANDARD PATENT

Invention Title:

RAPID LOAD CAPACITY TEST

The following statement is a full description of this invention, including the best method of performing it known to me/us:

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TITLE: RAPID LOAD CAPACITY TEST

BACKGROUND OF THE INVENTION;

1. Field of the invention:

[0001] This invention relates to a rapid load capacity test.

[0002] The invention relates, but is not limited to, a load capacity test for the foundations of buildings; and more particularly, to the load capacity of piers or piles supporting the foundations.

[0003] Throughout the specification, the term “piles” will be used to include both piers and piles, whether driven into the ground (e.g. by a pile-driving machine), screwed into the ground, or cast in-situ.

2. Prior art:

[0004] Piles, having (typically hollow) steel shafts, are used to support building constructions, more typically building slabs, and are screw-driven into the soils below the slabs to be constructed.

[0005] Screw piles have at least one helical screw- orflyte around the shafts, usually adjacent the digging point at the lower end of the shafts. The helical screws- or flytes may be provided at spaced locations along the shafts, to spread the load transfer from the piles to the surrounding soil.

[0006] Engineers are always concerned that the load-bearing strength of the piles is sufficient to support the building constructions, in both static- and dynamic-load conditions. In cyclonic areas, wind forces can apply both lateral and vertical-uplift loads on a building construction, and so the load-bearing strength of the piles is not the only factor to be taken into account when specifying the piles and their locations under the building.

[0007] To enable the engineers to establish the load bearing capacity of the piles at a particular site, they typically have at least one test hole drilled to determine the soil profile and load capacity. However, as the soil structure may markedly vary within 30 cm (or less) of the test hole e.g, with an increased sand or clay content, the engineer must assume the soil structure is uniform over the site.

[0008] As structural failure is a greater concern than structural cost to the

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2013213724 20 Dec 2017 engineer, the resultant specification ofthe piles, and their location, is likely to be much greater than is necessary to achieve the desired load bearing capacity.

[0009] Alternatively, if the test hole indicated the soil structure is stronger I more stable than the remainder of the site, the “over-specification based in the test hole may actually result in “under-specification” for the balance ofthe site.

[0010] Many geographical areas in Australia, including Adelaide, have reactive soils, typically containing a high clay content. It is not unknown for such reactive soils to be liable to vertical “heave” exceeding 30cm between fully dry and fully wet.

[0011] The ‘heave” ofthe reactive soils has resulted in damage to building foundations, and to vertical displacement of a building relative to adjacent facilities / utilities.

[0012] It has been known, however, that the “heave” ofthe reactive soils e.g.

following rain after a long period of drought, has been so large as to raise the piles in the soil.

OBJECTS OF THE PRESENT INVENTION:

[0013] It is hoped that the present invention may overcome, or at least ameliorate, at least some of the problems of the prior art.

[0014] Other objects ofthe invention may become apparent from the following description.

SUMMARY OF THE PRESENT INVENTION:

[0015] In one aspect, the present invention resides in a method fortesting the load-bearing capacity of a pile, or for confirming that the pile meets a required load-bearing capacity, when the pile is in situ in the ground, the method including the steps of:

a) placing a frame of a load capacity test rig, which is supportable on the ground, over or in alignment with the in situ pile to be tested, such that a base of the frame substantially surrounds the pile;

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b) connecting a hollow ram jack, as a load-applicator on the test rig, to the pile using a connection apparatus, the connection apparatus including a lifting rod or bar passing through the hollow ram jack and connected at its upper end to a piston rod of the jack and connected at its lower end to the pile by a screw5 threaded or other releasable connection;

c) applying an up-lifting load to the pile using the load-applicator;

d) measuring the up-lifting load applied to the pile by the load-applicator or calculating the up-lifting load applied to the pile by the load-applicator. [0016] [Blank] [0017] [Blank] [0018] In a second aspect, the present invention resides in an apparatus for testing the load-bearing capacity of a pile, or for confirming that the pile meets a required load-bearing capacity, when the pile is in situ in the ground, the apparatus including:

a frame supportable on the ground over or in alignment with the in situ pile to be tested, the frame having a base that substantially surrounds the pile; a hollow ram jack, as a load-applicator, on the frame;

a connection apparatus to connect the load-applicator to the pile, the connection apparatus including a lifting rod or bar passing through the hollow ram jack and connected at its upper end to a piston rod of the jack and connected at its lower end to the pile by a screw-threaded or other releasable connection; and measuring and/or indication apparatus to measure an up-lifting load applied to the pile by the load-applicator and/or to provide an indication that enables calculation of the up-lifting load applied to the pile by the ioad-applicator.

[0019] Preferably, the jack may be a hollow ram hydraulic jack or a hollow ram pneumatic jack with an annular cylinder, and the piston rod of the jack may also be annular, and the lifting rod or bar may be received through the piston rod and cylinder.

[0019a] The piston rod of the jack may be connected to the upper end of the lifting rod or bar by a screw-threaded connection.

[0020] The upper end of the lifting rod or bar may be secured to the piston rod

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2013213724 20 Dec 2017 of the jack by an abutment washer and a high tensile nut.

[0021] The base of the frame may be substantially annular and able to be positioned in coaxial alignment with the in situ pile.

[0021a] The frame may include a pad to which the jack is mounted, and the pad may be supported above the base of the frame by a plurality of struts. [0022] Preferably, the measuring and/or indication apparatus used includes a sensor to measure the hydraulic pressure applied to the load-applicator; and a gauge or indicator connected to the sensor indicates the hydraulic pressure, the measured up-lift force applied to the pile and/or the calculated load10 bearing capacity of the pile.

BRIEF DESCRIPTION OF THE DRAWING:

[0023] To enable the skilled workman to fully understand the invention, and to enable that person to put the invention into practice, preferred embodiments will now be described with reference to the accompanying drawing, in which: FIG. 1 is a schematic side view of the testing of a blade pile in accordance with a first embodiment of the present invention.

[0024] Any annotations on FIG. 1 are by way of illustration only, and are not limiting to the scope of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS:

[0025] The blade pile 10 schematically illustrated in FIG. 1 is representative of all screw- or blade piles, where a hollow steel shaft 11 is terminated at a digging point or tip 12, and one or more pairs of screws or blades 13 are provided on the shaft. The skilled addressee will be aware that the pairs of screws or blades 13 may be provided at spaced intervals up the shaft 11; and that stabilising fins (not shown) may be provided about the shaft 11 to increase the lateral stability of the pile 10.

[0026] A load-bearing capacity test apparatus 20, to test the load-bearing capacity of the pile 10, has a transportable test rig 30 which can be moved from pile to pile 10 to be tested on-site.

[0027] The test rig 30 has a frame 31, with a substantially annular base plate,

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4a or feet 32, at the lower end of a plurality of spaced steel struts 33, which support a substantially annular pad 34 at their upper ends. The base plate, or feet 32, are arranged to enable the test rig 30 to be slid laterally into co-axial alignment with the pile shaft 11.

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2013213724 07 Aug 2013 [0028] A hollow hydraulic ram jack 40 is mounted co-axially on the annular pad 34. The ram jack 40 is connected to a (high-pressure) hydraulic pump 50 via hydraulic hoses 51, 52 and pressure gauge 53.

[0029] The hydraulic ram jack 40 has an annular cylinder 41 and an annular piston rod 42.

[0030] A lifting rod 60 is received co-axially within a central passage 43 through the piston rod 42 (and cylinder 41 ). The lifting rod 60 is screwthreaded at least at its respective upper and lower ends 61, 62.

[0031] The upper end 61 of the lifting rod 60 is secured to the distal end of the piston rod 42 by an abutment washer 63 and high tensile nut 64.

[0032] The lower end 62 of the lifting rod 60 is connected to the upper end 14 of the pile shaft 11 by a releasable coupling apparatus 70.

[0033] In the embodiment illustrated in FIG. 1, the coupling apparatus 70 includes a screw-threaded nut insert 71 secured in the upper end 14 of the pile shaft 11.

[0034] In an alternative embodiment, not shown, lugs or fingers may be provide on the exterior of the upper end 14 of the pile shaft 11, or internally in the upper end 14 of the pile shaft 11, and be releasably engaged by a complementary bayonet-type coupling at the lower end 62 of the lifting rod

60; or vice versa.

[0035] In other alternative embodiments, one or more transverse locking pins may releasably connect the lower end 62 of the lifting rod 60 to the upper end 14 of the pile shaft 11; the lifting rod 60 and pile shaft 11 may be screwthreadably coupled together; or a wedge-type connection e.g. with balls or rollers in an annular coupling head, may couple the lifting rod 60 and the pile shaft 11.

[0036] The skilled addressee will appreciate that there are many possible releasable coupling methods to connect the lifting rod 60 to the pile shaft 11. [0037] The skilled addressee will also appreciate that the hollow hydraulic ram jack 40 may be substituted by one or more hydraulic-, pneumatic- or mechanical screw jack(s), which may be connected to the upper end 61 of the lifting rod 60 by a lifting-head, lifting-yoke or like device to spread the load

2013213724 07 Aug 2013 between the jacks.

[0038] The skilled addressee will further appreciate that two or more lifting rods may interconnect the lifting-head, lifting-yoke or like device to a coupling apparatus connectable to the upper end 14 of the pile shaft 11. With this arrangement, it is preferable that the coupling apparatus be releasably connectable to the exterior of the pile shaft 11.

[0039] In a further alternative embodiment not illustrated, the lifting rod (or rods) may be connected to (e.g. the distal end of) a lever arm, or rocker arm, pivotally mounted on the frame 31 and selective raised by one or more jacks.

[0040] In use, the test rig 30 is located with the lifting rod 60 co-axially aligned with the pile shaft 11. The lower end 62 of the lifting rod 60 is coupled to the upper end 14 of the pile shaft 11 by screw-threaded engagement between the lower end 62 of the lifting rod 60 and the nut insert 71.

[0041] The hydraulic pump 50 is operated to supply hydraulic fluid, of increasing pressure, to the hydraulic lift jack 40, causing the piston rod 42 to apply a lifting load to the lifting rod 60, which transfers the lifting load to the pile shaft 11.

[0042] The operator monitors the hydraulic pressure via the gauge 53, and can calculate the lifting force being applied to the pile 10. By use of the conversion uplift-force = 70% (load-bearing capacity), the operator can calculate the load-bearing capacity of the pile 10. (The skilled addressee will appreciate that the gauge can be calibrated to directly indicate the uplift force applied to pile 10 and/or the load-bearing capacity of the pile 10; or that the hydraulic pressure may be measured by a sensor, where the output is fed to a computer for calculation / display I recordal of the load-bearing capacity for each specific pile.

[0043] The operator can either determine the absolute load-bearing capacity of the pile 10; or test to ensure the load-bearing capacity of the pile is within design limits e.g. 8 tonnes.

[0044] When the particular pile 10 has been tested, the hydraulic pressure is reduced and the test rig 30 is disconnected from the pile. It can now be easily moved about the site to test another selected pile 10. This means that several

2013213724 07 Aug 2013 pilesl 0 can be quickly tested on a site to determine the soil structure(s) on the site, and their load-bearing characteristics.

[0045] By use of the test method and apparatus of the present invention, the engineer can quickly, and accurately, establish the load-bearing capabilities of the soil structures at multiple locations across a site, rather than simply relying on a single test result as representative of the whole site. This means that an engineer may be able to specify lighter-construction piles and/or fewer piles to achieve the design load for the piles supporting the building construction. [0046] In addition, if the testing method provides markedly varying measured load-bearing capacities, the engineer can immediately request that additional piles be tested e.g. in a location where the largest variations occur. The additional tests can be quickly, and relatively inexpensively, carried out. [0047] The engineer is more confident that the foundation design, supported by the piles, is appropriate for the building construction, as changes in the soils structure / characteristics can be compensated for e.g. where the site covers both reactive and no-reactive soils.

[0048] Various changes and modifications may be made to the embodiments described and illustrated without departing from the present invention.

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Claims

CLAIMS:

1. A method for testing the load-bearing capacity of a pile, or for confirming that the pile meets a required load-bearing capacity, when the pile

5 is in situ in the ground, the method including the steps of:

a) placing a frame of a load capacity test rig, which is supportable on the ground, over or in alignment with the in situ pile to be tested, such that a base ofthe frame substantially surrounds the pile;

b) connecting a hollow ram jack, as a load-applicator on the test rig, to 10 the pile using a connection apparatus, the connection apparatus including a lifting rod or bar passing through the hollow ram jack and connected at its upper end to a piston rod ofthe jack and connected at its lower end to the pile by a screw-threaded or other releasable connection;

c) applying an up-lifting load to the pile using the load-applicator;

15 d) measuring the up-lifting load applied to the pile by the loadapplicator or calculating the up-lifting load applied to the pile by the loadapplicator.
2. An apparatus for testing the load-bearing capacity of a pile, or for

20 confirming that the pile meets a required load-bearing capacity, when the pile is in situ in the ground, the apparatus including:

a frame supportable on the ground over or in alignment with the in situ pile to be tested, the frame having a base that substantially surrounds the pile; a hollow ram jack, as a load-applicator, on the frame;

25 a connection apparatus to connect the load-applicator to the pile, the connection apparatus including a lifting rod or bar passing through the hollow ram jack and connected at its upper end to a piston rod of the jack and connected at its lower end to the pile by a screw-threaded or other releasable connection; and

30 measuring and/or indication apparatus to measure an up-lifting load applied to the pile by the load-applicator and/or to provide an indication that enables calculation of the up-lifting load applied to the pile by the load3478869v1

2013213724 20 Dec 2017 applicator.
3. The method of claim 1, or the apparatus of claim 2, wherein the jack is a hollow ram hydraulic jack or a hollow ram pneumatic jack with an annular

5 cylinder, and the piston rod of the jack is also annular, and the lifting rod or bar is received through the piston rod and cylinder.
4. The method of claim 1 or 3, or the apparatus of claim 2 or 3, wherein the piston rod of the jack is connected to the upper end ofthe lifting rod or bar

10 by a screw-threaded connection.
5. The method or apparatus of claim 4 wherein the upper end ofthe lifting rod or bar is secured to the piston rod of the jack by an abutment washer and a high tensile nut.
6. The method of any one of claims 1 or 3-5, or the apparatus of any one of claims 2 or 3-5, wherein the base of the frame is substantially annular and able to be positioned in coaxial alignment with the in situ pile.

20 7. The method of any one of claims 1 or 3-6, or the apparatus of any one of claims 2 or 3-6, wherein the frame includes a pad to which the jack is mounted, and the pad is supported above the base ofthe frame by a plurality of struts.

25 8. The method of any one of claims 1 or 3-7, or the apparatus of any one of claims 2 or 3-7, wherein:

the measuring and/or indication apparatus used includes a sensor to measure the hydraulic pressure applied to the load-applicator; and a gauge or indicator connected to the sensor indicates the hydraulic

30 pressure, the measured up-lift force applied to the pile and/or the calculated load-bearing capacity ofthe pile.

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FIG. 1